I believe I would say this is the best Mario game ever and a real contender for game of the year.
The level design is amazing in SMG. Each level is on different planets and none feel alike for the most part. The graphics are beautiful. You might question why we had to go to high def when you play this game. Actually what makes the graphics so good is the art work. The amount of thought that went into each level is astounding. Also a player will not become bored because every level can be finished rather quickly. I found this to be very enjoyable because I always felt like I was making progress. The story is very Mario esque. Bowser is trying to control the galaxy and has kidnapped the princess. So you must resue Peach and save the galaxy. Also the Wii controls are implemented nicely. Nintendo didn't overdo it and what they did added to the gameplay.
Overall I think SMG ranks as one of the best games of 2007 and for the first time I actually enjoyed a Mario game as much as a Zelda. If you own a Wii then this game needs to be part of your collection.